从维基百科表中抓取网址

Question

我试图刮取页面https://en.wikipedia.org/wiki/UEFA_Euro_2012_squads并可以使用rvest取消文本数据

library(plyr)
library(XML)
library(rvest)
library(dplyr)
library(magrittr)
library(data.table)

for(i in 1:16)
{
float <- paste("squad", i, sep ="")
print(float)
html = read_html("https://en.wikipedia.org/wiki/UEFA_Euro_2012_squads")
assign(float, html_table(html_nodes(html, "table")[[i]]))
}

但是也想在俱乐部的每张桌子上添加一个额外的栏目.例如对于小队1(页面上的波兰小队,截断以显示前5名球员)

     0#0 Pos.              Player                    Date of birth (age) Caps Goals                Club
1   1  1GK  Wojciech Szczęsny    (1990-04-18)18 April 1990 (aged 22)   11     0             Arsenal
2   2  2DF  Sebastian Boenisch  (1987-02-01)1 February 1987 (aged 25)    9     0       Werder Bremen
3   3  2DF Grzegorz Wojtkowiak  (1984-01-26)26 January 1984 (aged 28)   19     0        Lech Poznań
4   4  2DF    Marcin Kamiński  (1992-01-15)15 January 1992 (aged 20)    3     0        Lech Poznań
5   5  3MF       Dariusz Dudka  (1983-12-09)9 December 1983 (aged 28)   65     2             Auxerre
6   6  3MF     Adam Matuszczyk (1989-02-14)14 February 1989 (aged 23)   20     1 Fortuna Düsseldorf

我希望在"clubURL"的"俱乐部"后面有一个专栏,可以显示该俱乐部的维基百科网址.例如,第一个球员为阿森纳效力,所以要把桌面上的链接用于阿森纳并创建:

0#0 Pos.             Player                 Date of birth (age) Caps Goals    Club
1   1  1GK Wojciech Szczęsny (1990-04-18)18 April 1990 (aged 22)   11     0 Arsenal
                                     clubURL
1 https://en.wikipedia.org/wiki/Arsenal_F.C.

等等等等.我发现rvest table scraping包括链接但是无法让这个例子起作用,也不能用我想做的事情.对不起,如果有人问过其他地方,

谢谢,

Answer 1

我使用页面上的第一个表格做了一个例子.您可以根据需要进行扩展.

首先,抓住第一个表并使用保存html_table.然后我创建了一个辅助函数,在给定链接文本的情况下从表中提取链接.然后我习惯sapply在数据框中填充一个新列.

library("rvest")
url <- "https://en.wikipedia.org/wiki/UEFA_Euro_2012_squads"
mytable <- read_html(url) %>% html_nodes("table") %>% .[[1]] 
df <- mytable %>% html_table()

get_link <- function(html_table, team){
  html_table %>% 
    html_nodes(xpath=paste0("//a[text()='", team, "']")) %>% 
    .[[1]] %>% 
    html_attr("href")
}

df$club_link <- sapply(df$Club, function(x)get_link(mytable, x))
> head(df)
  0#0 Pos.              Player
1   1  1GK  Wojciech Szczęsny
2   2  2DF  Sebastian Boenisch
3   3  2DF Grzegorz Wojtkowiak
4   4  2DF    Marcin Kamiński
5   5  3MF       Dariusz Dudka
6   6  3MF     Adam Matuszczyk
                     Date of birth (age) Caps Goals
1    (1990-04-18)18 April 1990 (aged 22)   11     0
2  (1987-02-01)1 February 1987 (aged 25)    9     0
3  (1984-01-26)26 January 1984 (aged 28)   19     0
4  (1992-01-15)15 January 1992 (aged 20)    3     0
5  (1983-12-09)9 December 1983 (aged 28)   65     2
6 (1989-02-14)14 February 1989 (aged 23)   20     1
                 Club                     club_link
1             Arsenal            /wiki/Arsenal_F.C.
2       Werder Bremen        /wiki/SV_Werder_Bremen
3        Lech Poznań        /wiki/Lech_Pozna%C5%84
4        Lech Poznań        /wiki/Lech_Pozna%C5%84
5             Auxerre              /wiki/AJ_Auxerre
6 Fortuna Düsseldorf /wiki/Fortuna_D%C3%BCsseldorf